Biomarkers of adverse reproductive outcomes are being applied by epidemiologists for surveillance of environmental hazards. Although a number of reproductive disorders can now be detected by these biomarkers, the biomarkers themselves do not identify the adverse outcomes as resulting from a toxic exposure, as opposed to a spontaneous abnormality. The epidemiologic study design provides information linking cause and effect by including appropriate control groups and simultaneous exposure assessment. Nevertheless, biomarkers of adverse effects have the potential to provide information on the period of time in which an environmental exposure may have occurred, as well as its health effect. Our objectives in the continuation of the Program Project are: 1) To study target organs in the reproductive tract that are the surface of altered biomarkers and the periods of time in the menstrual cycle and during pregnancy when these target organs may be vulnerable to environmental hazards. 2) To characterize patterns of biomarker response that follow exposure to environmental hazards during the menstrual cycle and during pregnancy, and determine the mechanisms in target cells by which these biomarkers are affected. In the next project period, we will accomplish these goals in four related but separate projects supported by two service cores. The primary Specific Aims of the Program Project in the next project period are: 1) To test the hypothesis that environmentally-induced perturbations of the hypothalamic-pituitary- ovarian axis during the late luteal phase of the menstrual cycle lead to increased bone loss in the subsequent cycle. This hypothesis will be tested directly in population-based studies and verified in experiments with the non-human primate model. 2) To utilize the ratio of bioactive to immunoreactive hCG (B:I ratio) as a biomarker for identification of normal pregnancies that are at risk for adverse effects of subsequent toxic exposures, and to test the hypothesis that changes in the hCG: B:I ratio identify a period of failing pregnancy which precedes the pregnancy loss. This hypothesis will be tested directly in population-based studies and verified with experiments in the non-human primate model. 3) To utilize TCDD as a model compound to investigate the ovary and the placenta as major targets of toxicity to human granulosa lutein cells and human trophoblast cells. These mechanistic studies will focus on TCDD-induced alterations in the production of hormones which are the biomarkers of ovarian and placental function. Our long term objective is to develop a comprehensive understanding of the value and limitations of endocrine biomarkers for detecting adverse reproductive outcomes that result from exposures to environmental agents. To accomplish this objective, we have assembled a team of fourteen investigators representing the primary disciplines which are the focus of this research (reproductive toxicology, epidemiology, reproductive biology, reproductive medicine) as well as related areas (endocrinology, developmental biology, cell biology, molecular biology) which will be critical for support of these studies.